PFMEA - RPN - Severity, Occurrence and Detection - Which one does not change?

[Roypeng]

Hi, there,

I had a job interview this afternoon, and they asked me such a question: Which one is not changed, among the the three items: severity, occurrence and detection?

Any comments or suggestions are welcome.

Roy

 

[Al Rosen]

Severity does not change.

 

[Roypeng]

Severity does not change.

Thank you, Al Rosen.

Roy

 

[Bill Ryan - 2007]

Just a little more......

The reason Severity doesn't change is that it takes a design change to affect the Severity rating which, ultimately, comes from the DFMEA. Things you do to monitor process paramaters will affect the Occurrence ratings and the inspections you perform (or don't perform) will affect the Detection ratings on the PFMEA.

 

[Rob Nix]

Good additional information Bill. However, to clarify further: both the actions "monitoring" and "inspecting" affect detection only. The actions that affect occurrence are changing the process (e.g. error-proofing) or the design (e.g. opening up tolerances, changing geometry).

I agree that "severity" is the one that doesn't change in a PFMEA, unless the product design is changed.

 

[Roypeng]

Thank you all for the additional information.

 

[astudent]

Unfortunately I have not the original version of the AIAG manual, but one translated in Italian and this bothers me a lot!
(but why is it not distributed for free?)
So, many times its difficult for me to cite parts of the document.
Anyway I will try to referr to the manual.
It seems to me that for both (S) and (E) [points 12 and 15] the documents says that these values can be modified by changing either the process or the design.
Am I wrong?
If so, where is the difference?

 

[deepak69748]

Hi, there,

I had a job interview this afternoon, and they asked me such a question: Which one is not changed, among the the three items: severity, occurrence and detection?

Any comments or suggestions are welcome.

Roy

severity does not change easily as seveity requires a design change

 

[Hennie]

severity does not change easily as seveity requires a design change

Severity relates to consequence of error/failure. How can a design change change this?

 

[Jim Wynne]

Severity relates to consequence of error/failure. How can a design change change this?

If you're filling the balloons at a children's birthday party with methane, the consequences of popping a balloon using a match can be made less severe by using helium.